Java网络编程之UDP和TCP实现

TCP协议需要在双方之间建立连接，通过输入输出流来进行数据的交换，建立需要通过三次握手，断开需要四次挥手，保证了数据的完整性，但传输效率也会相应的降低。

简单的TCP实现

//服务端 public class TcpServer { public static void main(String[] args) throws IOException { ServerSocket serverSocket = new ServerSocket(8886); // 建立服务端，ip为本机ip,端口为8886 Socket accept = serverSocket.accept(); // 监听客户端的连接，一旦有客户端连接，则会返回客户端对应的accept InputStream in = accept.getInputStream(); //获取到客户端的输出流 byte b[] = new byte[1024]; int len = in.read(b); System.out.println("接受到客户端数据,返回数据"+new String(b,0,len)); OutputStream out = accept.getOutputStream(); // 给客户端发送消息 out.write("服务端已经接受".getBytes()); serverSocket.close(); } } // 客户端 public class TcpClient { public static void main(String[] args) throws IOException { Socket socket = new Socket("127.0.0.1", 8886); // 通过Socket来建立和服务端的连接 OutputStream out = socket.getOutputStream(); // 获取输出流（客户端输出流即向服务端输出信息） out.write("hello tcp Server".getBytes()); // 输出信息 InputStream in = socket.getInputStream(); // 接受服务端的消息 byte b[] = new byte[1024]; int len = in.read(b); System.out.println("接受到服务器消息 ： "+new String(b,0,len)); // 输出 out.write("返回的的数据已经收到 ".getBytes()); // 向服务器返回消息 socket.close(); } }

改进服务端，启用多线程来接受客户端的数据

// server public static void main(String[] args) throws IOException { ServerSocket serverSocket = new ServerSocket(8886); // 建立服务端，ip为本机ip,端口为8886 int i=4; while(i>2){ Socket accept = serverSocket.accept(); // 监听客户端的连接，一旦有客户端连接，则会返回客户端对应的accept ServerThread st = new ServerThread(accept); // 启动线程 Thread th = new Thread(st); th.start(); } serverSocket.close(); } // thread public class ServerThread implements Runnable { private Socket accept; public ServerThread(Socket s) { this.accept = s; } public void run(){ InputStream in; try { in = accept.getInputStream(); byte b[] = new byte[1024]; int len = in.read(b); System.out.println("接受到客户端数据,返回数据" + new String(b, 0, len)); OutputStream out = accept.getOutputStream(); // 给客户端发送消息 out.write("服务端已经接受".getBytes()); } catch (IOException e) { e.printStackTrace(); } } }

传递图片

// 服务端 public class Server { public static void main(String[] args) throws IOException { ServerSocket serverSocket = new ServerSocket(5555); Socket ss = serverSocket.accept(); BufferedInputStream br = new BufferedInputStream(ss.getInputStream()); BufferedOutputStream bw = new BufferedOutputStream(new FileOutputStream("copy.jpg")); // 写出文件流 byte b[] = new byte[1024]; int len = 0; while ((len = br.read(b)) != -1) { // 写出文件 bw.write(b, 0, len); bw.flush(); // 别忘了刷新，要不然最后一块缓冲区字符串会缺失 } BufferedWriter bw2 = new BufferedWriter(new OutputStreamWriter(ss.getOutputStream())); // 输出 bw2.write("图片传输成功"); bw2.flush(); bw.close(); ss.close(); } } // 客户端 public class Client { public static void main(String[] args) throws UnknownHostException, IOException { Socket socket = new Socket("127.0.0.1", 5555); BufferedInputStream in = new BufferedInputStream(new FileInputStream("c.jpg")); BufferedOutputStream out = new BufferedOutputStream(socket.getOutputStream()); byte b[] = new byte[1024]; int len = 0; while ((len = in.read(b)) != -1) { out.write(b, 0, len); out.flush(); // 刷新缓冲区 要不然最后一块缓冲区字符串会缺失 } socket.shutdownOutput(); // 关闭流以后Server段才会接收道结束字符结束接受 BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream())); String line; while ((line = br.readLine()) != null) { System.out.println(line); } in.close(); socket.close(); } } UDP实现

UDP是将数据打成数据包向对方发送，只关系是否发送成功，而不关心是否接收成功，传输速度快，但是可靠性低。